Objectives: 1) To evaluate diagnostic techniques for B. pertussis in relation to the stage of illness and to discern which techniques provide optimal recognition of B. pertussis infection. 2) To determine the reservoir of B. pertussis infection and to assess the significance of adult transmission to infants. 3) To better understand the serologic response to contact with B. pertussis, and to discern which antibodies are important for immunoprotection. To date, six index cases and 19 household contacts have been enrolled and evaluated. Nasopharyngeal specimens have been processed with routine culture medium and direct fluorescent assay. In addition, newly developed techniques have been used with the clinical specimens. These include mouse monoclonal antibodies, developed in the Laboratory of Pertussis, for the immunofluorescent assay, and serologic methods to detect pertussis-specific antibodies. No additional recruitment occurred in FY92. IgG and IgA antibodies to PT, FHA, pertactin and fimbriae as well as total IgA and total protein were measured in serum and saline of the study population. Pertussis-specific IgA antibodies were routinely detected in saliva of both infected individuals, as well as symptomatic and asymptomatic household contacts, indicating that B. pertussis infection elicits a mucosal immune reponse in humans.